濾波器選擇與設計：系統性能的網關

　　通常，設計師要花那么多的時間專注于其復雜的規范和選擇成本較高的設備，如處理器、FPGA與ADC，他們沒有充分考慮到的主要性能的影響，以及成本和功耗問題，這是由選擇和整合的所謂“低端“部件如過濾器。

　　事實上，濾波器電路的規格和設計常常是決定整個系統成功的最重要因素。例如，如果在相對低帶寬應用中的濾波設計不能消除信號鏈前端的高帶寬噪聲，則系統必須燒毀額外的能量，以將不必要的噪聲傳播到信號鏈上?；蛘?，在處理某些帶寬的信號時，例如在基于信道的無線電接收機中，不適當的濾波設計會導致從相鄰信道的信號進行不必要的處理。這就導致了電源的浪費和目標信號的潛在退化。

　　Proper filter design also prevents the signal path from contributing noise to other parts of the system， such as keeping high-frequency signals from coupling back into the power circuit and causing instability or fluctuations. In essence， bypass capacitors are actually the simplest category of analog filters and are widely used in all types of designs.

　　Below is a brief overview of the role of filters， the types of filters， and differences between digital and analog approaches as well as between passive and active filtering designs. Then there are some specific design tips for simulating and selecting analog filters for an example application to drive high-performance analog-digital converters （ADCs）。